Flow controller - A closed-loop device that sets, measures and controls the flow of a particular gas or liquid.http://www.advanced-energy.com/upload/file/white_papers/sl-mfcfund-270-01.pdfFlow sensor - Utilize heat transfer principle to determine the flow velocity of fluid in pipe. As the fluid passes across the sensor, heat is carried from the sensor to the medium.http://www.ist-usadivision.com/sensors/flow/Level controller - Monitor liquid levels in vessels, and send out either pneumatic (typically 6 - 15 psig) or electric (typically 4 - 20 mA) signals to either the main control system, a local control system, or directly to an automated control valve.http://www.circorenergy.com/valves/liquid-level-controllers.phpLevel sensor - Classifies based on the specific application of the sensor. Sensors used for measurement of fluid levels.http://www.engineersgarage.com/articles/what-is-level-sensorComposition controllerComposition analyzer controllerFlow meter - A device used to measure the flow rate or quantity of a gas or liquid in the pipe.http://www.maxmachinery.com/what-is-a-flow-meterPressure transmitter - Converts pressure into an analog electrical signal achieved by the physical deformation of strain gages which are bonded into the diaphragm of the pressure transducer and wired into a wheatstone bridge configuration.http://www.omega.com/prodinfo/pressuretransducers.htmlPressure controller - To limiting or determining the pressure of the hydraulic system so that the equipment in motion is able to perform a certain function and keeping system pressures safely below a desired upper limit to maintaining a ser pressure in part of a circuit.http://hydraulicspneumatics.com/200/TechZone/HydraulicValves/Article/False/6411/TechZone-HydraulicValveshttp://demec.ufpr.br/reterm/ed_ant/10/artigo/technol07.pdf